Cyclopentadiene and alkylated derivatives thereof are known in the art. Further, methods are known for preparation of alkylated cyclopentadienes. There is substantial interest in cyclopentadienes since this material is characterized by the unique property of being the most acidic aliphatic hydrocarbon known, having a pKa of 18 and also because its reactions as a Diels-Alder diene are extremely facile.
Because of the aromaticity of the cyclopentadiene anion, cyclopentadiene is easily the most acidic of the simple hydrocarbons and in fact is comparable in acidity to alcohols. This means that substantial amounts of the anion can be generated with alkyl oxides and even concentrated solutions of hydroxide. Since it is uniquely stable, it can participate in the caranion reactions of alkylation, acylation, carboxylation and the like.
U.S. Pat. No. 3,255,267 to Fritz et al. discloses the alkylation of cyclopentadiene and monoalkylcyclopentadiene with a single primary or secondary alcohol in the presence of a highly alkaline catalyst, including the disclosure of trialkylated and tetralkylated products. The cyclopentadienes described by Fritz et al contain primary hydrocarbon substituents of up to 11 carbon atoms and secondary hydrocarbons of structure R.sub.c R.sub.d CH, where R.sub.d is "a hydrocarbon radical free of aliphatic unsaturation, including alkyl and aryl radicals, said radicals having from 1 to 10 carbon atoms,". However, the process of Fritz cannot be used to produce t-alkyl substituted cyclopentadienes.
In a publication by Rong et al, Acta Chemica Sinica, Vol. 41, No. 10, October, 1983, there is disclosure of the use of polyethylene glycol as a phase transfer agent for halide alkylation of cyclopentadiene with alkyl halides. The products produced are monoalkyl substituted cyclopentadienes. In a related article by Rong et al, Journal of Chinese Universities, Vol. 4, pages 576-580 (1983), there is disclosure of the synthesis of alkyl substituted derivatives of cyclopentadiene by the phase transfer catalytic reaction of cyclopentadiene with alkyl halides in the presence of potassium hydroxide and polyoxyethylene surfactants as a catalyst. Only monoalkyl substituted cyclopentadienes are prepared.
U.S. Pat. No(s). 3,004,384, 3,356,704, 3,358,008, 3,388,180, 3,391,209, 3,414,626, and 3,419,622 disclose polysubstituted cyclopentadienes and cyclopentadienes but wherein the substituent is a short chain alkyl group or allyl group. U.S. Pat. No(s). 3,751,500 and 3,636,176 disclose indene compounds which can contain short chain alkyl substituents which are useful as perfume compositions.
U.S. Pat. No. 2,448,641 discloses the alkylaton of cyclic hydrocarbons by reaction of a cyclic hydrocarbon such as a cycloolefin with an olefin such as ethylene in the presence of heat, pressure and a metallic sodium catalyst.
U.S. Pat. No. 2,276,203 discloses the condensation of allyl halides with substituted allyl halides in the presence of alkali metal amides.